Teaching transmission lines: a project of measurement and simulation

A junior-year project for a course in electromagnetic waves is described, including the theory, hardware, and basic measurements. The essence of the project is to simulate transmission- line properties based upon theory developed in the classroom and to measure those properties in the laboratory for comparison. The equipment chosen is readily available and inexpensive, but is used here to illustrate concepts usually requiring an expensive vector network analyzer. The transmission-line properties of insertion loss, input impedance, and crosstalk are measured as a function of frequency on Category 5 cable. The transmission-line phase shift, propagation velocity, attenuation, characteristic impedance, impedance under various transmission-line configurations, and crosstalk are modeled and measured. Measured and theoretical results are in good agreement, reinforcing the strength of the underlying theory for the student. Evaluation of the project over a three-year period with more than 120 students is very positive in terms of developing confidence in and understanding of this abstract material.